Self-defence is everyone’s right. Based on this right, one can defend himself against any eminent threat, even if it cause the predator’s death. This ethical principle is an applicable principle in ethics in war. However, the principle of self-defence has been applied in other situation such as justification of abortion if mother’s life is threatened by her fetus. Judith Thompson is a philosopher who defend abortion by applying this principle, in her book, “ A Defence of Abortion” Thompson categorized pregnancy into two types, wanted and unwanted pregnancy, argues that abortion is justified in wanted pregnancy if mother’s life is endanger. She also discusses the involvement of a third party in performing abortion. However, her argument has been criticised by her proponents as well as opponent. This article examines the principle of self-defence and its application in justifying abortion as well as the involvement of a third party in Thompson’s perspective.